Volume 21, Issue 6, Pages 875-881 (June 2013) Report of the wwPDB Small-Angle Scattering Task Force: Data Requirements for Biomolecular Modeling and the PDB  Jill Trewhella, Wayne A. Hendrickson, Gerard J. Kleywegt, Andrej Sali, Mamoru Sato, Torsten Schwede, Dmitri I. Svergun, John A. Tainer, John Westbrook, Helen M. Berman  Structure  Volume 21, Issue 6, Pages 875-881 (June 2013) DOI: 10.1016/j.str.2013.04.020 Copyright © 2013 Elsevier Ltd Terms and Conditions

Figure 1 Roadmap of SAS Data Collection and Analysis Scattering data are measured for a biologic macromolecule in solution on a two-dimensional detector as a circularly symmetric pattern. Data reduction (e.g., corrections for detector sensitivity, linearity, and circular averaging) yields a one-dimensional scattering profile for the macromolecule after subtraction of the solvent contribution to the scattering. The resultant SAS profile can be analyzed to provide overall structural parameters (Rg and molecular weight, MW) and P(r) versus r (which also yields the maximum dimension Dmax). After validation that the scattering particle has the expected MW, comparison can be made with a scattering profile calculated from a PDB coordinate file. Ab initio methods can provide bead or dummy-residue models indicating the shape of the macromolecule. In cases where structures of domains or subunits are known, rigid-body refinement can provide an atomistic model. SAXS data enable single phase modeling, while contrast variation data from SANS experiments enable multiphase modeling. If there are regions of the molecule of unknown structure, these can be modeled using a combination of rigid-body/dummy-residue modeling. Superposition of bead and rigid-body models is one form of model validation. Structure 2013 21, 875-881DOI: (10.1016/j.str.2013.04.020) Copyright © 2013 Elsevier Ltd Terms and Conditions